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.Dd November 8, 2021
.Dt VOP_ALLOCATE 9
.Os
.Sh NAME
.Nm VOP_ALLOCATE
.Nd allocate storage for a file
.Sh SYNOPSIS
.In sys/param.h
.In sys/vnode.h
.Ft int
.Fo VOP_ALLOCATE
.Fa "struct vnode *vp"
.Fa "off_t *offset"
.Fa "off_t *len"
.Fa "int ioflag"
.Fa "struct ucred *cred"
.Fc
.Sh DESCRIPTION
This call allocates storage for a range of offsets in a file.
It is used to implement the
.Xr posix_fallocate 2
system call.
.Pp
Its arguments are:
.Bl -tag -width offset
.It Fa vp
The vnode of the file.
.It Fa offset
The start of the range to allocate storage for in the file.
.It Fa len
The length of the range to allocate storage for in the file.
.It Fa ioflag
Directives and hints to be given to the file system.
.It Fa cred
The credentials of the caller.
.El
.Pp
The
.Fa offset
and
.Fa len
arguments are updated to reflect the portion of the range that
still needs to be allocated on return.
A partial allocation is considered a successful operation.
The file's contents are not changed.
.Sh LOCKS
The file should be exclusively locked on entry and will still be locked on exit.
.Sh RETURN VALUES
Zero is returned if the call is successful, otherwise an appropriate
error code is returned.
.Sh ERRORS
.Bl -tag -width Er
.It Bq Er EFBIG
An attempt was made to write a file that exceeds the process's file size
limit or the maximum file size.
.It Bq Er ENOSPC
The file system is full.
.It Bq Er EPERM
An append-only flag is set on the file, but the caller is attempting to
write before the current end of file.
.El
.Sh SEE ALSO
.Xr vnode 9 ,
.Xr VOP_READ 9 ,
.Xr VOP_WRITE 9
